PHOENIX (AP) — Police say loud barking might have led a 56-year-old man to kill four of his neighbors and two dogs before turning the weapon on himself over the weekend at a central Phoenix town house.

There is "some indication that perhaps that was a problem," Phoenix police Sgt. Tommy Thompson said Sunday of the barking. But he added a motive might never be known because of the deaths.

Michael Guzzo, 56, killed four members of a family in the confrontation Saturday. The victims were identified as Bruce Moore, 66; his daughter, Renee Moore, 36; her husband, Michael Moore, 42, who took his wife's name; and Renee's son, Shannon Moore, 17.

After the killings, Guzzo shot at another town house before returning to his unit and killing himself, police said.

Police said they found a pump shotgun, apparently the weapon used in the killings, next to his body. Thompson said there was no indication he had a violent past.

A neighbor said Guzzo usually kept to himself.

"I've seen him every morning — come in quiet every morning," Donald McKenzie told Phoenix television station KSAZ-TV. "Never would expect him to be the guy who did this at all."

Another neighbor, Barry Hatchett, told Phoenix station KNXV-TV he was friends with Renee Moore. Hatchett said he had planned to take his dog to the Moores' home for a grooming appointment later Saturday.

After shooting the Moores and the dogs, Guzzo walked across the large complex and shot at the door and second floor of another town house, police said.

KNXV-TV reports the second home belongs to Libni DeLeon, who said bullet holes are now scattered around his house.

DeLeon told the station he heard a knock Saturday morning before the gunman shot through his front door.

"I ran upstairs and when I got there I got a glance at him, and I yelled at him, and he turned around and shot two more rounds upstairs," DeLeon said.

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